Continuous mixing reactor and method of use

ABSTRACT

A continuous mixing reactor has an outer shell having a cylindrical portion with a central section and two opposite conical end sections; a circulation tube within the shell so that an annular passage forms between the shell and the circulation tube; an impeller within and positioned adjacent to one end of the circulation tube; and heat exchange means penetrating the outer shell and extending into the end of the circulation tube opposite the impeller. The outer shell has a hydraulic head forming one end of the shell, a heat exchange medium header at the opposite end of the shell. The circulation tube nearer the heat exchange medium header terminates at or downstream from a tangential plane extending through the shell at the intersection of the central section and the conical end section of the cylindrical portion of shell. The reactor is useful in an alkylation process.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation of application Ser. No. 14/262,167filed Apr. 25, 2014 which claims priority of U.S. Patent Application61/816,373 filed Apr. 26, 2013, the contents of both applications areincorporated herein by reference in their entirety for all purposes.

FIELD OF THE INVENTION

The present invention relates to a continuous mixing reactor and methodof use, for example, in an alkylation process.

BACKGROUND OF THE INVENTION

A continuous mixing reactor is a reaction vessel that has a continuousmixer having internal circulation, wherein circulation is provided by animpeller. The reactor is a horizontal pressure vessel having an outershell, an inner circulation tube, a mixing impeller, and an indirectheat exchange provided by a tube bundle. These reactors are suitable forcarrying out chemical reactions under conditions providing intimatecontact between reactants, in a single phase or in multiple phases.Continuous mixing reactors are known, and examples can be found asdescribed in U.S. Pat. Nos. 3,759,318 and 3,965,975.

Basic operation of a continuous mixing reactor includes:

-   1. The continuous mixing reactor shell serves to contain the    reaction mixture.-   2. The circulation tube serves to establish an internal flow path in    the reactor (down the center of the circulation tube and through an    annular passage which exists between the circulation tube and the    shell).-   3. The shell has a hydraulic head, which contains shaft sealing    means and any required bearings for the impeller shaft. The    hydraulic head also incorporates a reversal zone for flow of fluid    from the impeller.-   4. The impeller effects mixing and circulation in the reactor. A    mixing circulating impeller provides high shear and turbulence to    reactants to maximize rate.-   5. Indirect heat exchanging means provided as a tube bundle    containing a heat exchanging medium for addition or removal of heat    absorbed or generated during the reaction. Temperature control is    achieved by addition or removal of reaction heat by heat exchange    throughout a reaction zone in the reactor. Tube bundles may be of    the U-tube type, bayonet tube or others.

The conventional flow path within a continuous mixing reactor, startingfrom the discharge side of the impeller, is through a reversal area in ahydraulic head, thereafter through an annular passage between thecirculation tube and the outer shell, at the end of the circulation tubethrough a reversal area in the end of the reactor opposite the impeller,and finally through the center of the tube bundle, that is, the centralsection of the reactor, within the circulation tube back to theimpeller. Reactants are normally fed as near as possible to the eye ofthe impeller so that they are immediately and thoroughly mixed anddispersed into the main body of the reaction mix.

The design of a continuous mixing reactor is to maximize circulation andturbulence of the internal fluids.

An example of a process performed in a continuous mixing reactor isalkylation. In an alkylation process light olefins (such as propylene,butylenes, amylenes) are reacted with an isoparaffin (branched alkane),such as isobutane, in the presence of an acid catalyst such as sulfuricacid, to form an alkylate product. The alkylate product is a mixture ofgasoline boiling range branched hydrocarbons, which can be blended witha refinery gasoline pool, to increase the gasoline octane and reduce thevapor pressure.

In an alkylation process, olefin and isoparaffin are combined in a feed,which is injected into a suction side of the impeller inside thecirculation tube. The impeller rapidly disperses the feed within theacid catalyst to form an emulsion. The emulsion is circulated by theimpeller at high rates within the reactor.

Tube wear has been found in continuous mixing reactors havingconventional flow paths at the reversal area in the end of the reactoropposite the impeller. In an alkylation process, wear may be due tocorrosivity of acid catalyst, temperature and other factors. Flowdistribution in the reversal area creates pressure losses resulting inuneven flow to the center of the bundle.

It is desired to reduce and minimize tube wear of tubes in tube bundleheat exchanging means. For example reduce and minimize wear at the endof the circulation tube in a continuous mixing reactor, to moreefficiently use the heat exchange capacity of the tube bundle and toprovide better flow distribution in the tube bundle. The continuousmixing reactor and method disclosed herein meets these needs.

SUMMARY OF THE INVENTION

-   The present disclosure provides a continuous mixing reactor which is    a horizontal pressure vessel having    -   (a) an outer shell, wherein the outer shell has an interior wall        and an exterior wall; one or more inlets for fluids, a hydraulic        head (or circulating head) forming one end of the shell, a heat        exchange medium header at the opposite end of the shell from the        hydraulic head; wherein the shell has a generally cylindrical        portion between the hydraulic head and the heat exchange medium        header, having a central section and two opposite end sections,        the central section having a substantially uniform diameter and        each end section is a conical section, and a discharge outlet        positioned on a surface of the cylindrical portion; and    -   (b) a hollow circulation tube, open at both ends, extending from        the hydraulic head to a terminal end opposite of the hydraulic        head and nearer to the heat exchange medium header, and        positioned axially within the shell and spaced from the interior        wall thereof such that an annular passage is formed between the        circulation tube and the shell; and    -   (c) an impeller received within and positioned adjacent to the        end of the circulation tube within the hydraulic head of the        shell, wherein the impeller provides for mixing of fluid within        the reactor, creating a cyclic flow of fluids through said tube;        and    -   (d) heat exchange means penetrating the outer shell, wherein the        heat exchange means has a tube sheet extending from the head        exchange medium header into the open end of the circulation tube        opposite of the impeller, wherein the heat exchange means        penetrates substantially the length of the central section of        the cylindrical portion of the outer shell;        characterized as having (1) the end of the circulation tube        nearer to the heat exchange medium header terminate at or        downstream from (based on direction of flow of fluid through the        impeller through a reversal area in the hydraulic head then        through the annular passage between the shell and the        circulation tube) a tangential plane extending through the shell        at the intersection of the central section and the conical end        section of the cylindrical portion of shell; or (2) a flow        distribution plate attached to the terminal end of the        circulation tube.

The continuous mixing reactor disclosed herein is particularly suitablefor use in chemical reactions, such as, for example, an alkylationprocess, in particular, an acid-catalyst alkylation process.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a cross-section view of a continuous mixing reactor of theprior art, having a large, elongated U-section heat exchanging tubebundle penetrating the end of the circulation tube opposite the impellerand extending substantially the entire length thereof.

FIG. 2 is a view of the reactor of FIG. 1 showing a section of thereactor that includes the heat exchange medium header and flow ofliquid.

FIG. 3 is a cross-section view of a continuous mixing reactor asdisclosed herein showing a section of the reactor that includes the heatexchange medium header and flow of liquid.

DETAILED DESCRIPTION

The continuous mixing reactor disclosed herein is a generally horizontalreactor. The reactor has an outer shell to contain the reaction mixture;a circulation tube to establish an internal flow path in the reactor; animpeller for mixing; and heat exchange means for addition or removal ofheat of a reaction carried out within the reactor.

The reactor as disclosed herein has a conventional flow pattern. Thatis, fluids enter the reactor before the impeller through suitablenozzles. After mixing in the impeller, the mixed fluids flow through anannular space outside of the circulation tube and the outer shellthrough a reversal zone in which direction of fluid flow reverses in theend of the shell at the hydraulic head. Flow then proceeds through anannular passage between the circulation tube and the outer shell,thereafter through a second reversal zone in which direction of fluidflow reverses in the end of the shell opposite the hydraulic head. Fluidthen flows back to the impeller within the circulation tube and incontact with the heat exchange means.

A continuous mixing reactor of the present disclosure has an outer shellhaving interior and exterior walls. The shell has one or more inlets toallow introduction of fluids into the reactor. The shell has a hydraulichead that forms and closes one end of the shell. The hydraulic head hasa shaft sealing means and any required bearings for the impeller shaft.The head incorporates a reversal zone for flow of liquids from theimpeller as described and illustrated herein.

At the end of the shell opposite the hydraulic head is a heat exchangemedium header. This header provides for flow of coolant into and out ofthe heat exchange means described further below.

The shell has a generally cylindrical portion (cylinder) between thebetween the hydraulic head and the heat exchange medium header. Thecylindrical portion has a central section and two opposite end sections.The central section of the cylindrical portion is a tube havingsubstantially the same diameter along the length of the tube. Each endof the cylindrical portion is a conical section, that is, has aprogressively decreasing diameter in a direction away from the centralsection of the cylinder. That is, the cylindrical portion has a tube ofuniform diameter through the center of the reactor shell, and this tubetapers at both end sections as the cylindrical portion approaches thehydraulic head and the heat exchange medium header, at the respectiveends. The tapering may be uniform (concentric conical end section) ornon-uniform (eccentric conical end section). For example, a non-uniformtapering occurs when the bottom of the reactor fails to slope upward atthe same angle as the top of the reactor slopes downward, such asremains flat. (See FIG. 1.)

In one embodiment, the conical end section near the hydraulic head isconcentric. In one embodiment, the conical end section near the heatexchange medium header is concentric. In one embodiment at least one ofthe conical end sections is eccentric. In one embodiment both endsections are concentric. In one embodiment the end section near thehydraulic head is eccentric.

The shell also has a discharge outlet to allow for removal of materialfrom the continuous mixing reactor. The discharge outlet is located on asurface of the central section of the cylindrical portion of the outershell. The discharge outlet may be located on an upper (top) surface ofthe shell or on a lower (bottom) surface of the shell. The dischargeoutlet may be upstream of the conical end section near the heat exchangemedium header. In one embodiment, product is removed from a dischargeoutlet located on the top surface of the reactor.

The continuous mixing reactor disclosed herein has a hollow, open-endedcirculation tube positioned axially or concentrically within the shelland spaced from the interior wall of the shell, forming an annularpassage therewith. The circulation tube is generally congruent with theouter shell, such as with the cylindrical portion of the shell. One endof the circulation tube is near the hydraulic head of the shell. At thisend, the circulation tube may taper to maintain the annular passagethrough the conical section of the cylinder approaching the hydraulichead. The opposite end, referred to herein as the terminal end of thecirculation tube (away from the hydraulic head and nearer to the heatexchange medium header) terminates at or downstream from (based ondirection of flow of fluid through the impeller through a reversal areain the hydraulic head then through the annular passage between the shelland the circulation tube) a tangential plane extending through the shellat the intersection of the central section and the conical end sectionof the cylindrical portion of shell.

The continuous mixing reactor has an impeller received within the end ofthe circulation tube nearer to the hydraulic head. The impeller providesfor mixing and creating a cyclic flow of fluids through the tube and inthe annular passage surrounding said tube. The impeller is mounted on ashaft which rotates within in the hydraulic head. The hydraulic headforms the end of the shell adjacent to the impeller and contains shaftsealing means, such as suitable packing glands and any required bearingsfor the impeller shaft. The impeller is driven by a suitable primemover, such as a driving motor, turbine or engine.

The continuous mixing reactor has heat exchange means, which penetratesthe outer shell at the end of the shell opposite the impeller andextends from a tube sheet into the open end of the circulation tubeopposite of the impeller. The heat exchange means extends through theheat exchange medium header of the outer shell into the circulation tubesubstantially the length of the central portion of the cylindricalportion of the outer shell. The heat exchange means as disclosed hereincan have an elongated U-section heat exchanging tube bundle. Individualtubes of the tube bundle are rolled into or otherwise attached to a tubesheet, which closes in the heat exchange medium header. Tube bundles areillustrated in FIGS. 1-3 herein. An alternative form of heat exchangeris disclosed in U.S. Pat. No. 2,800,307. A typical heat exchange mediumheader having a central wall or partition therewithin dividing the tubeends from one another permits distribution of heating or cooling medium(coolant) to the tubes of the bundle.

Nozzles and/or feed lines are provided for feeding fluid, such asindividual fluid components or blended fluids or mixtures to becirculated into the continuous mixing reactor. The nozzles and/or feedlines extend both through the outer shell and inner circulation tubeupstream of flow into the impeller. The feeds and reaction mixture aredischarged into the circulation tube upstream of the impeller. Theimpeller is thus arranged for taking suction from the circulation tubeand discharging fluid into the hydraulic head. Within the latter, theflow of fluid is reversed in a reversal zone and flow is directed intothe annular passage between the outer shell and circulation tube.

In a conventional continuous mixing reactor, the circulation tubeextends from the impeller end toward the heat exchange medium header ofthe reactor. The terminal end of the circulation tube in a conventionalreactor terminates within the central section of the cylindrical portionof the outer shell, as referred to herein as a “non-extended”circulation tube. As shown in FIG. 2, there is created an annular regiondefined by the outer shell, the heat exchange means and the tube that isa stagnant area downstream of the circulation tube near the tube sheet.Neither fluid flow nor heat exchange is efficient in the annular region.

In the present disclosure, the circulation tube terminates at ordownstream of (based on direction of flow through the annular passage) atangential plane extending through the shell at the intersection of thecentral section and the conical end section of the cylindrical portionof the outer shell, and is referred to herein as an “extendedcirculation tube”—extended relative to the non-extended circulation tubein a conventional reactor. The size of the annular region as defined bythe outer shell, the heat exchange means and the tangential plan at theterminal end of the circulation tube is reduced relative to the size ofthis region in a conventional reactor. Fluid flow and heat exchange areimproved.

In one embodiment, the terminal end of the circulation tube terminatesat a tangential plane extending through the shell at the intersection ofthe central section and the conical end section of the cylindricalportion of shell. In one embodiment, the terminal end of the circulationtube terminates downstream from a tangential plane extending through theshell at the intersection of the central section and the conical endsection of the cylindrical portion of shell. In one embodiment, thedischarge outlet is located on an upper surface of the shell at orupstream of the intersection of the central section and conical endsection of the cylindrical portion of the shell nearer to the heatexchange medium header. In one embodiment, the terminal end of thecirculation tube terminates in an open end in advance of, upstream ofthe tube sheet.

In one embodiment of the disclosure, the reactor has a flow distributionplate attached to the terminal end of the circulation tube. The flowdistribution plate may be perforated. The flow distribution plate allowsfluid to pass from the circulation tube into the annular region wherereversal of fluid flow occurs.

In one embodiment of the disclosure, the terminal end of the circulationtube is located at a position at or downstream of (based on direction offlow through the annular passage) a tangential plane at the intersectionof the central section and conical end section of the cylindricalportion of the outer shell nearer to the heat exchange medium header,and within the terminal end of the circulation tube is provided a flowdistribution plate. Thus, in one embodiment, the circulation tube is anextended circulation tube having a flow distribution plate.

The continuous mixing reactor disclosed herein provides certainadvantages when used in an alkylation process. When the reactordisclosed herein is used in an alkylation process, advantages includebetter management of reaction temperature, more efficient use of heattransfer surface, decreased tube wear, better flow distribution to thecenter of the tube bundle, reduced size of annular region (as definedherein), which corresponds to less stagnant area for side reactions tooccur.

The continuous mixing reactor as disclosed herein is suitable processeshaving (1) a relatively large quantity of heat of reaction, as well as(2) a relatively large reaction time (residence time) requirement as maybe desired, for example in an alkylation process.

One embodiment of the disclosure is an alkylation process. An alkylationprocess comprises contacting at least one olefin with at least oneisoparaffin (reactant isoparaffin) in the presence of an acid catalystto produce a product comprising isoparaffins (product isoparaffins)wherein the contacting is performed in a reactor as described herein.One or more olefins can be used. One or more reactant isoparaffins canbe used to react with the olefin. The product isoparaffins have longercarbon chains than the reactant isoparaffins.

The olefin is a light olefin, generally a C₃ to C₅ olefin, such asisobutylene. One or more C₃ to C₅ olefins may be used. The reactantisoparaffin is generally a mixture of isoparaffins, for example, amixture of isoparaffins comprising isoparaffins having 5 to 16 carbonatoms.

Alkylation processes are catalyzed by acid. Any acid catalysts,homogeneous or heterogeneous, can be used in the invention. Examples ofsuitable acid catalysts include, but are not limited to, sulfuric acid,hydrogen fluoride, acidic ion exchange resin, zeolite, fluorosulfonicacid, boron trifluoride, antimony pentafluoride, phosphoric acid, metalhalide such as aluminum chloride and aluminum bromide, complex ofaluminum chloride and sulfuric acid, solid acid catalyst, andcombinations of two or more thereof. The catalyst can be sulfuric acidfor it is readily available and effective in alkylation.

Acid strength of the catalyst is preferably maintained to providesufficient catalytic activity. For example, the useful range forsulfuric acid can be generally in the range of about 86 to 99 weightpercent.

The volume ratio of catalyst to total hydrocarbon (olefin and reactantisoparaffins) can be generally in the range of from about 0.001:1 toabout 100:1, or about 0.1:1 to about 10:1, and or about 0.5:1 to about10:1. Normal operation of a reactor as disclosed herein for sulfuricacid-catalyzed alkylation service uses a target acid to hydrocarbonratio of 1:1. Ratio of acid to hydrocarbon may not range above 1.5:1,thus the volume ratio of catalyst to total hydrocarbon can be 1:1 to1.5:1.

The contacting of the olefin with the reactant isoparaffin can becarried out under conditions sufficient to alkylate the olefin(s). Suchconditions can include a temperature in the range of from about −40° C.to about 260° C., such as about −15° C. to about 95° C., or about 0° C.to about 55° C. under a pressure that can accommodate the temperaturerange such as, for example, about atmospheric to about 35 MPa, or in therange of about 65 to about 7000 kPa, or in the range of about 300 toabout 1750 kPa for a period of from about 1 second to about 100 minutes,or in the range of about 0.1 to about 30 minutes, or in the range ofabout 1 minute to about 20 minutes. In one embodiment, temperature is inthe range of about 4° C. to about 20° C. In one embodiment, pressure isin the range of about 340 to about 500 kPa.

The contacting is carried out in the continuous mixing reactor asdisclosed herein.

DETAILED DESCRIPTION OF THE FIGURES

FIG. 1 is a cross-section view of a continuous mixing reactor 10 of theprior art, illustrating elements of the reactor disclosed herein.Reactor 10 has reactor shell 11, hydraulic head 12 forming one end ofthe shell and heat exchange medium header 13 forming the opposite end ofshell 11. Reactor 10 has an elongated U-section heat exchanging tubebundle 14 which terminates in heat exchange medium header 13.

FIG. 1 also illustrates reactor 10 outer shell 11 having a generallycylindrical portion 15 between hydraulic head 12 and heat exchangemedium header 13, which tapers prior to each end. As illustrated,generally cylindrical portion 15 of outer shell 11 has a central section16 having a substantially uniform diameter that tapers into a concentricconical section 17 at heat exchange medium header 13 and into aneccentric conical section 18 at hydraulic head 12 at the opposite end ofshell 11. As will be appreciated by those skilled in the art, theconical sections may taper into either concentric conical sections oreccentric conical sections.

Circulation tube 19 is received within shell 11, with one open endpositioned within hydraulic head 12 and one open end opposite hydraulichead 12 (nearer to heat exchange medium header 13) positioned such thatcirculation tube 19 terminates upstream of (based on direction of flowof fluid through the annular passage 20 between shell 11 and circulationtube 19) a tangential plane 21 extending through shell 11 at theintersection of central section 16 and the conical section 17 ofcylindrical portion 15 of shell 11. Impeller 22 is positioned in openend of circulation tube 19 within hydraulic head 12. Motor 23 drivesimpeller 22. The end of circulation tube 19 opposite impeller 22 is alsoopen to permit fluid flow from annular passage through tube bundle 14.

FIG. 1 is illustrative of an alkylation process in which Acid (sulfuricacid) and HC (hydrocarbon) are fed to reactor 10 through inlets tocirculation tube 19 upstream of impeller 22. Fluid flows throughimpeller 22 into annular passage 20 between shell 11 and circulationtube 19 with flow around open end of circulation tube 19 nearest heatexchange medium header 13 and through tube bundle 14. Flow throughreactor 1 is illustrated by arrows.

Product emulsion exits reactor 10 at outlet 24 to an emulsion settler(not shown). Also, FIG. 1 designates coolant inlet 25 and outlet 26 oftube bundle assembly 14 in the heat exchange medium header 13.

FIG. 2 is an expanded view of the continuous mixing reactor of FIG. 1showing a portion of reactor 110 that includes heat exchange mediumheader 113. Solid arrows illustrate flow of fluid through annularpassage 120 between circulation tube 119 and shell 111 around open endsof circulation tube 119 and through tube bundle 114. Dashed arrowsillustrate flow of coolant through inlet 125 into heat exchange mediumheader 113 to tube bundle 114 and from tube bundle 114 through outlet126 of heat exchange medium header 113. Circulation tube 119 extendstoward heat exchange medium header 113 terminating upstream of atangential plane 121 extending through shell 111 at the intersection ofcentral section 116 and conical section 117 of cylindrical portion 115of shell 111. Annular region 130 shows an area of the reactor 110 wheretube bundle 114 cooling is under-utilized for lack of material flow.Outlet 124 is provided for product to exit reactor 110.

FIG. 3 is an expanded view of a continuous mixing reactor as disclosedherein showing a portion of reactor 210 that includes heat exchangemedium header 213. Solid arrows illustrate flow of fluid through annularpassage 220 between circulation tube 219 and shell 211 around open endsof circulation tube 219 and through tube bundle 214. Dashed arrowsillustrate flow of coolant through inlet 225 into heat exchange mediumheader 213 to tube bundle 214 and from tube bundle 214 through outlet226 of heat exchange medium header 213. Circulation tube 219 extendstoward heat exchange medium header 213 terminating at a tangential plane221 extending through shell 111 at the intersection of the centralsection 216 and conical section 217 of cylindrical portion 215 of shell211. Annular region 230 shows an area of reactor 210 where greaterutilization of cooling capacity of tube bundle 214 is achieve relativeto FIG. 2. Outlet 224 is provided for product to exit reactor 210.

EXAMPLES Example 1 and Comparative Example A

Flow distribution such as may occur in alkylation processes weresimulated based on reactors as shown in FIGS. 2 and 3 and analyzed usingCFD modeling in Comparative Example A (an embodiment of a reactor of theprior art) and Example 1 (an embodiment using a reactor as disclosedherein), respectively, using ANSYS Fluent CFD Software (ANSYS, Inc., 275Technology Drive, Canonsburg, Pa. 15317). The same conditions were usedfor simulations in reactors of FIG. 2 and FIG. 3.

The CFD results showed the improvement in flow distribution for thereactor as disclosed herein into stagnant regions near the tube sheet ofthe heat transfer medium, better flow distribution at the end of thecirculation tube (that is, flow not all turning at the end ofcirculation tube), and better flow distribution within the tube bundle,relative to flow in reactor of the prior art.

Example 2 and Comparative Example B

Alkylation processes were performed using the reactors as shown in FIG.2 (Comparative Example B, an embodiment using a reactor and process ofthe prior art) and FIG. 3 (Example 2, an embodiment using a reactor andprocess as disclosed herein). The same process conditions were used foran alkylation process using sulfuric acid as catalyst and C₃ to C₅olefin and a mixture of C₅ to C₁₆ isoparaffins. The target acid tohydrocarbon ratio was 1:1. The temperature was 4° C. to 20° C. (about40° F. to 65° F.) and the pressure was and 340 to 490 kPa (about 50 to70 psig).

Results found multiple benefits for using the reactor and process ofExample 2 relative to Comparative Example B. The benefits include:

-   -   10-12% increase in heat transfer values.    -   Approximately 3° F. (2.5° F. to 3.5° F. or 1.3 to 1.9° C.)        reaction temperature drop at a constant olefin flow rate or 9 to        12% olefin flow rate increase at constant reaction temperature.

Other benefits will of the reactor and process will be appreciated bythose skilled in the art.

What is claimed is:
 1. A continuous mixing reactor having (a) an outershell, wherein the outer shell has an interior wall and an exteriorwall; one or more inlets for fluids, a hydraulic head (or circulatinghead) forming one end of the shell, a heat exchange medium header at theopposite end of the shell from the hydraulic head; wherein the shell hasa generally cylindrical portion between the hydraulic head and the heatexchange medium header, having a central section and two opposite endsections, the central section having a substantially uniform diameterand each end section is a conical section, and a discharge outletpositioned on a surface of the cylindrical portion; and (b) a hollowcirculation tube, open at both ends, extending from the hydraulic headto a terminal end opposite of the hydraulic head and nearer to the heatexchange medium header, and positioned axially within the shell andspaced from the interior wall thereof such that an annular passage isformed between the circulation tube and the shell; and (c) an impellerreceived within and positioned adjacent to the end of the circulationtube within the hydraulic head of the shell, wherein the impellerprovides for mixing of fluid within the reactor, creating a cyclic flowof fluids through said tube; and (d) heat exchange means penetrating theouter shell, wherein the heat exchange means extends from the heatexchange medium header into the open end of the circulation tubeopposite of the impeller, wherein the heat exchange means penetratessubstantially the length of the central section of the cylindricalportion of the outer shell; characterized as having the end of thecirculation tube nearer to the heat exchange medium header terminates ator downstream from a tangential plane extending through the shell at theintersection of the central section and the conical end section of thecylindrical portion of shell.
 2. The reactor of claim 1 having the endof the circulation tube nearer to the heat exchange medium headerterminate at a tangential plane extending through the shell at theintersection of the central section and the conical end section of thecylindrical portion of shell.
 3. The reactor of claim 1 having the endof the circulation tube nearer to the heat exchange medium headerterminate downstream from a tangential plane extending through the shellat the intersection of the central section and the conical end sectionof the cylindrical portion of shell.
 4. The reactor of claim 1 whereinthe conical end section near the hydraulic head is concentric.
 5. Thereactor of claim 1 wherein the conical end section near the heatexchange medium header is concentric.
 6. The reactor of claim 1 whereinat least one of the conical end sections is eccentric.
 7. The reactor ofclaim 1 wherein both end sections are concentric.
 8. The reactor ofclaim 1 wherein the end section near the hydraulic head is eccentric. 9.The reactor of claim 2 having nozzles for feeding fluid into through theouter shell and circulation tube upstream of flow into the impeller. 10.The reactor of claim 3 having nozzles for feeding fluid into through theouter shell and circulation tube upstream of flow into the impeller. 11.The reactor of claim 2 having an annular region defined by the outershell, the heat exchange means and the tangential plane at the terminalend of the circulation tube.
 12. The reactor of claim 3 having anannular region defined by the outer shell, the heat exchange means andthe tangential plane at the terminal end of the circulation tube.
 13. Analkylation process comprising contacting an olefin with an isoparaffinin the presence of an acid catalyst to produce a product comprisingisoparaffins wherein the contacting is performed in a reactor as setforth in claim
 1. 14. An alkylation process of claim 13 wherein theolefin is one or more C₃ to C₅ olefin and the isoparaffin is a mixtureof isoparaffins.
 15. An alkylation process of claim 13 wherein the acidcatalyst is sulfuric acid, hydrogen fluoride, acidic ion exchange resin,zeolite, fluorosulfonic acid, boron trifluoride, antimony pentafluoride,phosphoric acid, metal halide such as aluminum chloride and aluminumbromide, complex of aluminum chloride and sulfuric acid, solid acidcatalyst, or a combination of two or more thereof.
 16. An alkylationprocess of claim 15 wherein the acid is sulfuric acid.
 17. An alkylationprocess of claim 16 having conditions of a temperature in the range offrom about −40° C. to about 260° C. and a pressure in the range of aboutatmospheric to about 35 MPa and a volume ratio of catalyst to totalhydrocarbon in the range of from about 0.001:1 to about 100:1.
 18. Analkylation process of claim 16 having conditions of a temperature in therange of from about −15° C. to about 95° C. and a pressure in the rangeof about 65 to about 7000 kPa and a volume ratio of catalyst to totalhydrocarbon in the range of from about 0.1:1 to about 10:1.
 19. Analkylation process of claim 16 having conditions of a temperature in therange of from about 4° C. to about 20° C. and a pressure in the range ofabout 340 to about 500 kPa and a volume ratio of catalyst to totalhydrocarbon (olefin and reactant isoparaffins) in the range of fromabout 1:1 to about 1.5:1.